Many types of retractable landing gear are kept in the deployed position by means of a folding strut having two arms which are hinged to each other and which are kept in a substantially aligned position by a stabilizing member. One of the arms is hinged to a barrel of the landing gear, while the other arm is hinged to the aircraft structure. When kept aligned in this way, the strut arms form a bracing structure, which immobilizes the landing gear in the deployed position.
As a general rule, the stabilizing member itself incorporates two rods hinged to each other, the two rods being pushed back by a spring member toward an aligned position in which they stabilize the arms of the strut in the aligned position. An unlocking actuator is used to break the alignment of the rods of the stabilizing member, thus breaking the alignment of the strut arms and allowing the landing gear to be raised by the action of a raising actuator, which, for example, acts directly on the barrel of the landing gear.
In a known form, the unlocking actuator is a telescopic actuator coupled at one end to the landing gear barrel or to one of the strut arms, and at the other end to one of the rods of the stabilizing member. When the landing gear is deployed from a stowed position to its deployed position, the telescopic unlocking actuator is normally free to extend or contract in accordance with the relative movements of the two parts to which it is coupled.
During the folding of the landing gear into the stowed position, the telescopic unlocking actuator should be activated in such a way that it breaks the alignment of the stabilizing rods. The raising actuator then takes over to move the landing gear toward its stowed position. The strut arms and the rods of the stabilizing member have relative rotary movements imparted to them during the raising of the landing gear, and they also impart telescopic movements to the telescopic unlocking actuator, as a result of which the telescopic actuator, if still active, may oppose the raising movement.
One immediate solution to this problem is to deactivate the telescopic unlocking actuator as soon as it has performed its function, in other words as soon as it has broken the alignment of the rods of the strut stabilizing member. However, this procedure requires a more complex raising logic with the provision of sensors positioned to detect when the alignment of the rods has been broken, making it necessary to provide wiring on moving parts of the landing gear to carry information from the sensors to the computer which implements the raising logic.